1. Field
One embodiment of the present invention relates to illumination and exposure techniques employed for projecting a pattern of a first plane onto a second plane, and is applicable when used for transferring a mask pattern onto a photosensitive substrate in a lithography step for manufacturing various devices such as semiconductor devices, liquid crystal display devices, and thin-film magnetic heads, for example.
2. Description of the Related Art
A double exposure method is one of exposure methods for transferring a pattern of a reticle as a mask onto a wafer (or glass plate or the like) coated with a photoresist, which is used when manufacturing a semiconductor device or the like. When a pattern in which periodic and isolated patterns are mixed is exposed to one layer on a wafer, for example, this technique divides the reticle pattern into a first pattern corresponding to the periodic pattern and a second pattern corresponding to the isolated pattern, and subjects these two patterns to double exposure while successively optimizing their exposure conditions, thereby yielding a high imaging performance. Such a double exposure method has conventionally carried out exposure by performing the first exposure by using a first reticle formed with one or a plurality of first patterns and then performing the second exposure by replacing the reticle with a second reticle formed with one or a plurality of second patterns. However, a high throughput cannot be obtained when carrying out the exposure by exchanging the reticles as such.
Therefore, an exposure method has been proposed in Japanese Patent Application Laid-Open No. HEI 11-111601, which forms a single reticle with first and second patterns beforehand, transfers the patterns of the reticle to first and second shot regions adjacent to each other on a wafer by a scanning exposure scheme, and then transfers the reticle patterns to the second and third shot regions on the wafer after moving the wafer stepwise by one shot region, thereby double-exposing the first and second patterns to the second shot region. By changing illumination conditions when illuminating the first and second patterns in a predetermined illumination region at the time of scanning exposure, this exposure method can optimize the illumination conditions for these two patterns.